Co-infection of fowl adenovirus with different immunosuppressive viruses in a chicken flock

In poultry, fowl adenovirus (FAdV) and immunosuppressive virus co-infection is likely to cause decreased egg production, inclusion body hepatitis, and pericardial effusion syndrome. In this study, fowl adenovirus infection was found in parental and descendent generations of chickens. We used quantitative polymerase chain reaction (PCR) and dot blot hybridization to detect the infection of reticuloendotheliosis (REV), avian leukosis virus (ALV), and chicken infectious anemia virus (CIAV) in 480 plasma samples. The test samples were 34.58% FADV-positive, 22.29% REV-positive, 7.5% CAV-positive, and 0.63% ALV-positive. Sequence analysis showed that FADV belonged to serotype 7, which can cause inclusion body hepatitis. The ALV strain was ALV-A, in which the homology of gp85 gene and SDAU09C1 was 97.3%. The positive rate was lower because of the purification of avian leukemia, whereas the phylogenetic tree analysis of REV showed that the highest homology was with IBD-C1605, which was derived from a vaccine isolate. Through pathogen detection in poultry we present, to our knowledge, the first discovery of fowl adenovirus type 7 infection in parental chickens and found that there was co-infection of FAdV and several immunosuppressive viruses, such as the purified ALV and CIAV. This indicates that multiple infection of different viruses is ever-present, and more attention should be given in the diagnosis process.